An internal combustion engine has an intake valve and an exhaust valve. Mixture gas of fuel and air is drawn into a combustion chamber of the engine through the intake valve. Combustion gas is exhausted through the exhaust valve. The intake valve and the exhaust valve open and close corresponding to a stroke of a piston axially moving in the combustion chamber of the engine.
A valve timing control apparatus is provided to an engine for enhancing fuel efficiency of the engine and for reducing emission from the engine. The valve timing control apparatus variably controls valve timing, when at least one of the intake valve and the exhaust valve opens and closes, in accordance with an operating condition of the engine.
The valve timing control apparatus includes a housing member and a rotor member that rotate relative to each other for controlling the valve timing. In general, one of the housing member and the rotor member rotates together with a cam and camshaft that actuates intake valve or exhaust valve of the engine. The other of the housing member and the rotor member is driven by a crankshaft of the engine. In general, a hydraulic pressure device is provided to control a relative angular position, i.e., relative phase between the housing member and the rotor member.
According to US2005/0252468A1 (JP-A-2005-325758), a valve timing control apparatus includes a housing member, a vane rotor, and a torsion coil spring. The torsion coil spring biases the vane rotor in a specific rotative direction with respect to the housing member. The housing member includes a shoe housing and a sprocket. The shoe housing has island portions each partitioning a hydraulic chamber in the shoe housing. The outer periphery of the rotor member (rotor vane) has vane portions each rotative in the hydraulic chamber relative to the housing member. The vane rotor has one axial end, to which a camshaft is fixed, and the other axial end, to which a spring plate (bushing vane) is provided.
In this valve timing control apparatus of US2005/0252468A1, a hydraulic device rotates the vane portion, accommodated in the hydraulic chamber, relative to the housing member, thereby controlling the relative phase between the crankshaft and the camshaft. Thus, the valve timing control apparatus controls the valve timing.
In this valve timing control apparatus, the vane rotor has one axial end having an engage hole in which the camshaft engages. The axes of the vane rotor and the camshaft are fixed by screwing a bolt. The vane rotor has the other end having an annular press-insertion hole, to which an end of a substantially cylindrical spring plate is press-inserted, so that the vane rotor is integrated with the spring plate. Specifically, first, the spring plate is integrated to the vane rotor, and subsequently, the camshaft is assembled to the vane rotor. When the spring plate is press-inserted into the press-insertion hole of the vane rotor, stress is applied to the vane rotor, and the stress further causes deformation in the engage hole axially on the opposite side of the press-insertion hole. The vane rotor has the thick portions, each having the vane portion, and the thin portions, each not having the vane portion. The thick portion and the thin portion are circumferentially arranged alternately one another. When the stress is applied to the vane rotor due to the press-insertion, the thin portion deforms substantially only in the vicinity of the press-insertion hole. However, in this press-insertion, the thick portion being high in rigidity broadly deforms therein, consequently, the deformation in the thick portion exerts influence to a distant portion such as the engage hole in the vane rotor. When the engage hole largely deforms, and the dimension of the engage hole is out of the dimensional tolerance thereof, the camshaft cannot be inserted properly into the engage hole.